This section provides background information related to the present disclosure which is not necessarily prior art.
Digital control techniques may be used to replace analog circuits in electronics products such as simple home appliances that may incorporate intelligence and remote control functions. These intelligent features require microprocessors, which need stable bias power. Digital controlled power supplies also need microprocessors or digital signal processors to be energized first in order to allow controlled operation.
It is challenging to get a low voltage bias (e.g., 3.3 V) directly from a utility grid supply (e.g., 115 VAC, 230 VAC, etc.). For example, a typical single phase household energy meter may need only about 10 mA at 3.3 V. A buck converter may require an extremely small duty cycle to produce such a low voltage bias from a utility grid supply. Many applications do not allow a low side control switch operation for a converter, and a high side switch operation requires a high side drive and related difficulties in sensing the output voltage directly for the regulation. Indirect feedback during the freewheeling period does not offer tight voltage regulation needed for microprocessors. Using an optocoupler for regulation adds to cost and complexity for low power needs.